This invention relates to a test device for monitoring one or more logic points in a circuit to determine the logic level or state thereof and to provide a display or indication of the state of each monitored point, and more particularly relates to a self-contained circuit including display elements responsive to the logic signals at respective logic points.
It is often important to determine whether one or more logic points in an overall logic circuit are at logic 0 or logic 1 levels for the purpose of determining proper circuit operation as well as to detect faults. Moreover, in view of the complexity of circuits especially in computers and the cost of computer time such determinations should be able to be made easily and rapidly.
Prior art devices for monitoring the logic level of one or more logic points have required, for example, transistorized circuitry including light emitting diode indicators as well as an external power supply for energizing such transistorized circuit. Although such prior art systems are effective to determine logic level, the individual transistorized circuits are themselves subject to possible failures due to the number of elements included in each and are often cumbersome due to the requirement for connection to an external power supply.